This invention generally relates to safety guards for cannular devices, and specifically to a cannula guard useful in taking blood donations, performing blood transfusions, administering medication or the like. The guard of the invention is characterized by an outer sheath member slidably disposed about the cannula. The outer sheath may be operably engaged with the cannula to facilitate insertion of the cannula into a patient, and when the cannula is withdrawn from the patient, the same motion retracts the cannula (including specifically the exposed distal tip thereof) within the outer sheath and accomplishes permanent retention of the distal tip within the outer sheath.
Numerous devices have been proposed to reduce the danger of handling potentially contaminated needles, cannulas and the like. It is well known that, for example, handling and disposal of used cannular needles exposes nurses, doctors and other persons to the risk that they will be pricked by the pointed, distal end of the needle and possibly become infected with AIDS or another disease.
Among the devices presently available to address this problem are U.S. Pat. Nos. 4,778,453 and 4,782,841 to Lopez, and U.S. Pat. No. 4,820,282 to Hogan. The Lopez patents disclose guards usable with hypodermic syringes and require that the needle assemblies be screwed onto the syringe. For that reason, the Lopez guards are not readily adaptable for use in cannular applications. Moreover, the devices of the Lopez patents leave a substantial portion of the used needle exposed to subsequent handlers of the assembly, and the '841 patent even leaves the proximate end of its needle 26 in a dangerously unprotected state after removal from the syringe.
The well-known use of "butterfly needles" is illustrated in the Hogan '282 patent. The guard of Hogan has significant shortcomings, however, including the facts that the guard is separate from the "butterfly" structure rather than being packaged and utilized as a single unit, and that the manipulation of the guard during its use may cause substantial, and predictably painful or uncomfortable, movement of the cannula within the patient's body.
Our invention, in contrast, provides the simplicity of a single unitized butterfly needle and guard, and accomplishes substantially complete coverage of the used needle virtually immediately upon withdrawal of the needle from the patient.